At cruise RPM (2500 or so) the terminal voltage of a fully-charged 6 volt battery should be approximately 7.5 volts. The final check will be how often water needs to be added to the cells. Overcharging will cause rapid water loss, and voltage regulator adjustment below about 7.25 volts will result in a chronically under-charged battery.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!